Compositions and devices for wound closures are well known. The most common being simple adhesive based strips, or bandages, such as BAND-AIDS®, or for more specialized purposes, sutures or staples. The application of sutures or staples typically requires a trained specialist and the procedures are invasive and painful and may require anesthetic. Moreover, those procedures often leave unsightly scars from secondary insertion holes and spacing and depth variation. Also, frequently follow-up visits to doctor or by other trained professional for removal is required. Simple bandages or BAND-AIDS often are not adequate to close and hold more severe or deeper wounds; and pulling off the bandage is painful.
Others have invented a wound closure device which comprises a series or array of microstructured needles affixed to a backing device. Using two spaced arrays, they may be positioned on opposite sides of the wound needing closure. These devices can be easily applied and removed with little pain, as no adhesive is used and the microneedles are inserted only to a depth of the upper epidermis that essentially is devoid of the pain-nerve endings.
The optimum length, sharpness and height of the microneedles has been a result of extensive study and it has been determined that microneedles that are bent (or curved, and for purposes of this application the term “bent” includes a smooth or radiused curve) provide the most desirable structure for both skin penetration and effectively anchoring or holding power over the wound at the stratum corneum. Also for purposes of this application the term micro-needle is all inclusive of various shapes and cross-sections of the needle, such as conical, pyramidal, blade, rectangle, or other variations, each ending with an elongated sharper end referenced as the tip which is intended to enter the skin adjacent the wound to be closed.
The density of the microneedles may be predetermined and may vary depending upon the size of the device and the wound to be closed, much as bandages vary in size and the location on the body where they are to be applied. For example the density may be 1 microneedle/cm2 to 1 microneedle/10 cm2. The pitch between adjacent microneedles may be from 30 μm to 1 cm, wherein pitch is defined as the distance between needles, center point to center point.
Because of the very small configuration of the microneedles in terms of reduced cross section from the base to the sharp tip, and the relative rigidity required to assure stability and anchoring of the device when installed over a wound, it has been very difficult to provide an economic and useful method for producing these devices having bent microneedles in an efficient and accurate manner.
The preferred materials for the device must be FDA approved polymers; one of the most useful for this purpose is PMMA. Others have tried to injection mold hooks using PMMA for Velcro® type hook and loop fasteners, but found that the PMMA was too stiff to be easily removed from the mold and still retain the necessary curvature.
While one may achieve a bent shape by possible reheating the hook, or forming the bent shape as the hook is formed, the high temperature necessary for bending needed at the middle of the needle could affect the sharpness of the tip.
WO 2010/140760 A2 describes using a curved substrate to attempt to angle micro-needles inward. But in order to replicate needle arrays from a mold, undercuts cannot be readily achieved.